Back to EveryPatent.com
United States Patent |
5,087,812
|
Tsukada
|
February 11, 1992
|
Incremental encoder with direction-indicating shutter
Abstract
A light-transmission-type encoder usable in, e.g., an image scanner, and
suitable for detecting both the amount of and the direction of rotation.
An image scanner featuring the encoder is used to read an image on an
original while utilizing the self-scanning direction of a self-scanning
image sensor as the main scanning direction and a direction substantially
perpendicular to the main scanning direction as the sub-scanning
direction, then transfer a read-image signal to image memory of a host
computer for recording and displaying. The encoder includes a rotary body
having peripheral slits permitting light transmission therethrough, a
shaft integrally supporting the rotary body, a shutter having a slit and
being loosely and swingably fitted on the shaft, a spring for causing
force of friction between either the shutter and the shaft or the shutter
and the rotary body, a first light-emitter and a first light-receiver
which are disposed with the rotary-body slits therebetween, and a second
light-emitter and a second light-receiver which are disposed with the
shutter slit therebetween. With this encoder, the image scanner detects
the direction of rotation of the rotary body from the relation in position
of the shutter slit with the second light-emitter and light-receiver, and
adjusts, in accordance with the detected direction, the position in which
the image signal is stored in the image memory.
Inventors:
|
Tsukada; Jiro (Wakuya, JP)
|
Assignee:
|
Alps Electric Co., Ltd. (Tokyo, JP)
|
Appl. No.:
|
606010 |
Filed:
|
October 30, 1990 |
Foreign Application Priority Data
| Nov 20, 1989[JP] | 1-133918[U] |
Current U.S. Class: |
250/231.14; 250/237G |
Intern'l Class: |
G01D 005/34 |
Field of Search: |
250/231.14,231.13,237 G,237 R
356/375
|
References Cited
U.S. Patent Documents
4533830 | Aug., 1985 | Beauprey | 250/231.
|
4559448 | Dec., 1985 | Rozsa | 250/231.
|
4847484 | Jul., 1989 | Kikuchi | 250/221.
|
4864125 | Sep., 1989 | Minami et al. | 250/231.
|
Primary Examiner: Nelms; David C.
Attorney, Agent or Firm: Shoup; Guy W., Kivlin; B. Noel
Claims
What is claimed is:
1. A light-transmission-type encoder including a rotary body having on its
periphery slits permitting light to be transmitted therethrough, said
encoder being adapted to detect both the amount of rotation and the
direction of rotation of the rotary body, said encoder comprising: a shaft
on which said rotary body is integrally mounted; a shutter loosely and
swingably fitted on said shaft; a spring for causing force of friction
between said shutter, on one hand, and either said shaft or said rotary
body, on the other; a first light-emitter and a first light-receiver which
are disposed with said slits of said rotary body positioned therebetween;
and a second light-emitter and a second light-receiver which are disposed
with said shutter positioned therebetween.
2. A light-transmission-type encoder according to claim 1, further
comprising a slit formed in said shutter, wherein said second
light-emitter and said second light-receiver are disposed with said slit
of said shutter positioned therebetween.
3. A light-transmission-type encoder according to claim 1, wherein said
shaft has a small-diameter portion on which said shutter is loosely fit,
and a large-diameter portion on which said rotary body is integrally
mounted, said shutter abutting on the stepped surface between said
small-diameter portion and said large-diameter portion.
4. A light-transmission-type encoder according to claim 3, further
comprising a spring seat provided on said shaft and at a position opposed
to and spaced from said large-diameter portion of said shaft, wherein a
spring for causing force of friction between said shaft and said shutter
is disposed in the space between said spring seat and said shutter.
5. An image scanner adapted to read an image while utilizing the
self-scanning direction of a self-scanning image sensor as the main
scanning direction and a direction substantially perpendicular to said
main scanning direction as the sub-scanning direction, and transfer a
signal indicative of the read image to image memory of a host computer so
as to allow the image to be recorded and displayed, said image scanner
comprising: a light-transmission-type encoder including a rotary body
having on its periphery slits permitting light to be transmitted
therethrough, a shaft on which said rotary body is integrally mounted, a
shutter loosely and swingably fitted on said shaft, a spring for causing
force of friction between said shutter, on one hand, and either said shaft
or said rotary body, on the other, a first light-emitter and a first
light-receiver which are disposed with said slits of said rotary body
positioned therebetween, and a second light-emitter and a second
light-receiver which are disposed with said shutter positioned
therebetween; said image scanner detecting the direction of rotation of
said rotary body on the basis of the relation in position of said shutter
with said second light-emitter and said second light-receiver, and
adjusting, in accordance with the detected direction of rotation, the
position in which a signal indicative of the read image is stored in said
image memory so as to allow a display of the image as it is in the correct
positional relation with the image on the original irrespective of the
direction of movement of the scanner body.
6. An image scanner according to claim 5, further comprising a slit formed
in said shutter, wherein the image scanner detects the direction of
rotation of said rotary body on the basis of the relation in position of
said slit of said shutter with said second light-emitter and said second
light-receiver.
7. An image scanner according to claim 5, wherein said first light-emitter
and said first light-receiver are integrally incorporated in a first
detector, and said second light-emitter and said second light-receiver are
integrally incorporated in a second detector.
8. An image scanner according to claim 7, wherein said first detector is
mounted on a substrate and covered with a chassis, and wherein, as said
shutter swings, an end portion of said shutter abuts on either said
substrate or said chassis.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light-transmission-type encoder and an
image scanner having a light-transmission-type encoder. More specifically,
the present invention relates to a light-transmission-type encoder that
can be manufactured at relatively low cost and that is suitable for
detecting both the amount of rotation and the direction of rotation, and
an image scanner having such a light-transmission-type encoder.
2. Description of Related Art
Hitherto, encoders of a two-phase type have been known, which includes a
rotary body having a first position information pattern disposed radially
at a constant pitch from an annular common pattern described
concentrically with respect to a rotary shaft, and a second position
information pattern shifted in phase by a 1/4 pitch from the first
position information pattern, and which is adapted to detect both the
amount of and the direction of rotation.
Such a two-phase type encoder detects the first position information
pattern with a first detecting body, and detects the second position
information pattern with a second detecting body, so as to obtain two
pulse signals shifted from each other in phase by 90 degrees. The encoder
counts the pulses of the pulse signals so as to output a signal indicative
of the number of revolutions of the rotary shaft during forward and
backward rotation of the shaft. The encoder also outputs a signal
indicative of the direction of rotation of the rotary shaft from a
difference signal expressing the difference (in phase) between the two
pulse signals.
Referring to FIGS. 5 (a) and 5 (b), there are shown different relations
between reading and displaying which can be established when a
conventional image scanner reads an original.
In the reading shown in FIG. 5 (a), a conventional image scanner 41 is
manually moved by the user, who is also depressing a reading start switch
42 of the scanner 41, on an original 43 in a certain direction, e.g., from
above to below as viewed in FIG. 5 (a), whereby the scanner 41 reads an
image 44 on the original 43 sequentially in the direction indicated by an
arrow A. Then, the image 44 read from the original 43 is stored into an
image memory 47 of a host computer 46 connected with the scanner 41 via a
cable 45. The stored image is either displayed on a monitor 48 or output
as hard copy by a printer, not shown.
In the above-described image scanner 41, the main scanning direction is set
as the self-scanning direction of a self-scanning image sensor (not
shown), while the sub-scanning direction is set as a direction
substantially perpendicular to the main scanning direction, that is, as
the direction in which the entire image scanner 41, i.e., the scanner 41
body, is moved by the user. While the image scanner 41 reads an image 44
on an original 43 as described above, a single-phase encoder (not shown)
incorporated in the main body of the image scanner 41 detects the amount
of movement of the image scanner 41 body and outputs a signal indicative
of this detection.
Because the above-described conventional encoder requires both the first
position information pattern and the second position information pattern,
the rotary body of the encoder tends to become large. Further, in order to
accurately detect the shift in phase between these position information
patterns, the encoder must be manufactured with a relatively high level of
precision. Therefore, the encoder cannot be manufactured with ease, nor
can it be mass-produced efficiently. The large size of the rotary body and
poor mass-producibility of the encoder inevitably entail high production
cost. In order to improve the level of precision with which the encoder is
manufactured, it is possible to employ larger position information
patterns without making larger the rotary body. However, since the number
of patterns provided inevitably decreases, it becomes necessary to
increase the rotational speed of the rotary body. For this purpose, a
special mechanism for transmitting rotary force must be provided, but with
the risk that the rotary force transmitting mechanism may add noise
generated by the entire device, and the risk that additional space as well
as additional production cost for the mechanism may be necessary.
In the reading by the scanner 41 shown in FIG. 5 (b), the image scanner 41
body is moved in the direction opposite to the above, i.e., from below to
above as viewed in FIG. 5 (b), and an image 44 on an original 43 is read
sequentially as indicated by an arrow B. Since the encoder of the image
scanner 41 is single-phase-type, the read image is stored in the memory 47
in its state of being inverted as compared to the case shown in FIG. 5
(a). Also, the monitor 48 displays an image 44a which is vertically
inverted. In order to overcome this problem, it is possible to employ a
two-phase-type encoder in the image scanner. However, incorporating a
two-phase-type encoder involves the need to use a larger rotary body, and
other risks, thereby failing to sufficiently overcome the problem.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described
circumstances. A primary object of the present invention is to provide a
light-transmission-type encoder that is capable of detecting both the
amount of rotation and the direction of rotation, yet has improved
mass-producibility and has a compact rotary body.
A second object of the present invention is to provide a compact image
scanner that is capable of providing a display image which is always in
correct, or non-inverted, positional relation with the original image.
In order to achieve the primary object, according to a first aspect of the
present invention, there is provided a light-transmission-type encoder
including a rotary body having on its periphery slits permitting light to
be transmitted therethrough, the encoder being adapted to detect both the
amount of rotation and the direction of rotation of the rotary body. The
encoder comprises: a shaft on which the rotary body is integrally mounted;
a shutter having a slit and being loosely and swingably fitted on the
shaft; a spring for causing force of friction between the shutter, on one
hand, and either the shaft or the rotary body, on the other; a first
light-emitter and a first light-receiver which are disposed with the slits
of the rotary body positioned therebetween; and a second light-emitter and
a second light-receiver which are disposed with the slit of the shutter
positioned therebetween.
In order to achieve the above-stated second object, according to a second
aspect of the present invention, there is provided an image scanner
adapted to read an image while utilizing the self-scanning direction of a
self-scanning image sensor as the main scanning direction and a direction
substantially perpendicular to the main scanning direction as the
sub-scanning direction, and transfer a signal indicative of the read image
to image memory of a host computer so as to allow the image to be recorded
and displayed. The image scanner comprises: a light-transmission-type
encoder including a rotary body having on its periphery slits permitting
light to be transmitted therethrough, a shaft on which the rotary body is
integrally mounted, a shutter having a slit and being loosely and
swingably fitted on the shaft, a spring for causing force of friction
between the shutter, on one hand, and either the shaft or the rotary body,
on the other, a first light-emitter and a first light-receiver which are
disposed with the slits of the rotary body positioned therebetween, and a
second light-emitter and a second light-receiver which are disposed with
the slit of the shutter positioned therebetween; the image scanner
detecting the direction of rotation of the rotary body on the basis of the
relation in position of the slit of the shutter with the second
light-emitter and the second light-receiver, and adjusting, in accordance
with the detected direction of rotation, the position in which a signal
indicative of the read image is stored in the image memory so as to allow
a display of the image as it is in the correct positional relation with
the image on the original irrespective of the direction of movement of the
scanner body.
With the above-specified construction of the light-transmission-type
encoder according to the present invention, when the shaft rotates, the
rotary body, which is integral with the shaft, rotates together with the
shaft, while the shutter, which is loosely fit on the shaft and is urged
by the spring to generate force of friction between the shutter and either
the shaft or rotary body, swings in agreement with the direction of
rotation of the shaft and the rotary body. The first light-emitter and the
first light-receiver, which are disposed with the slits of the rotary body
positioned therebetween, cooperate with each other to sense the passage of
the slits, then to output a signal indicative of the amount of rotation.
On the other hand, the second light-emitter and the second light-receiver,
which are disposed with the slit of the shutter positioned therebetween,
cooperate with each other to sense the position of the swinging shutter,
then to output a signal indicative of the direction of rotation. On the
basis of the rotation-amount signal and the rotation-direction signal, it
is possible to detect both the amount of and the direction of the rotation
of the rotary body. Since the rotary body does not have any position
information patterns of two types, the rotary body can be compact.
Further, there is no need to give consideration to the shift in phase
between the position information patterns, the level of precision with
which the encoder must be manufactured can be relatively low, thereby
improving the mass-producibility of the encoder.
With the above-described construction of the image scanner according to the
present invention, the image scanner reads an image while the
self-scanning direction of a self-scanning image sensor is used as the
main scanning direction and a direction which is substantially
perpendicular to the main scanning direction and in which the scanner body
is moved is used as the sub-scanning direction, then outputs a signal
indicative of the read image. At this time, the light-transmission-type
encoder operates, in the same manner as above, to detect both the amount
of and the direction of rotation, that is, to detect the amount of and the
direction of the movement performed by the image scanner relative to the
original in the sub-scanning direction, then outputs detection signals.
Subsequently, the image signal is stored, in accordance with the detection
signals, in image memory of the associated host computer. The data
expressed by the image signal stored in the image memory are read from the
memory while maintaining their relative position, then the read data are
output as a displayed image. Therefore, it is possible to obtain a
displayed image which is always in the correct positional relation with
the image on the original irrespective of the direction in which the image
scanner is moved.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view showing the construction of the essential parts of
one embodiment of a light-transmission-type encoder according to the
present invention;
FIG. 2 is a side view of the light-transmission-type encoder;
FIG. 3 is a vertical sectional view of one embodiment of an image scanner
according to the present invention;
FIG. 4 is a front view showing the construction of that part of the image
scanner enclosed by broken lines in FIG. 3; and
FIGS. 5 (a) and 5 (b) are views showing different relations between reading
and displaying which can be established during the reading of a
conventional image scanner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of a light-transmission-type encoder and an image
scanner having the encoder, both according to the present invention, will
be described with reference to the accompanying drawings.
FIG. 1 shows, in a front view, the construction of the essential parts of
an embodiment of a light-transmission-type encoder according to the
present invention, and FIG. 2 is a side view of the encoder.
The light-transmission-type encoder according to this embodiment includes,
as shown in FIG. 1, a rotary body 2 having, on the periphery thereof,
slits 1 permitting light to be transmitted therethrough, a shaft 3 on
which the rotary body 2 is integrally mounted, and a shutter 4 being
loosely and swingably fitted on the shaft 3 and having a slit 4. The
encoder also includes, as shown in FIG. 2, a spring seat 6 secured to the
shaft 3 and disposed as opposed to and spaced from the shutter 5, a spring
7 interposed between the shutter 5 and the spring seat 6 for causing force
of friction between the shutter 5 and the shaft 3, a first light-emitter
and a first light-receiver, such as a light emitting diode 8 and a
photo-transistor 9, which are disposed with the slits 1 of the rotary body
2 positioned therebetween, and a second light-emitter and a second
light-receiver, such as a light emitting diode 10 and a photo-transistor
11, which are disposed with the slit 4 of the shutter 5 positioned
therebetween. The shaft 3 has a small-diameter portion 3a on which the
shutter 5 is loosely fitted, and a large-diameter portion 3b on which the
rotary body 2 is integrally mounted. The shutter 5 is biassed by the
spring 7 in such a manner as to abut on the stepped surface between the
small-diameter portion 3a and the large-diameter portion 3b.
With the above-described construction of the encoder, when the shaft 3
rotates, the rotary body 2, which is integral with the shaft 3, rotates
together with the shaft 3, while the shutter 5, which is loosely fitted on
the small-diameter portion 3a of the shaft 3 and is urged by the spring 7
interposed between the shutter 5 and the shaft 3 to generate force of
friction therebetween, swings in agreement with the direction of rotation
of the shaft 3. The range of swinging of the shutter 5 is limited by a
stopper, not shown. The light-emitting diode 8 and the photo-transistor 9,
which are disposed with the slits 1 of the rotary body 2 positioned
therebetween, cooperate with each other to sense the passage of the slits
1 of the rotary body 2, then to output a rotation-amount signal from the
photo-transistor 9. On the other hand, the light-emitting diode 10 and the
photo-transistor 11, which are disposed with the slit 4 of the shutter 5
positioned therebetween, cooperate with each other to sense the position
of the swinging shutter 5, then to output a rotation-direction signal from
the photo-transistor 11.
Therefore, with the above-described embodiment, it is possible to detect
both the amount of and the direction of the rotation of the shaft 3 on the
basis of a rotation-amount signal output from the photo-transistor 9, and
on the basis of a rotation-direction signal from the photo-transistor 11,
respectively. Since the rotary body 2 does not have any position
information patterns of two types, but it has only the slits 1, the rotary
body 2 can be compact. Further, the slits 1 do not involve the need to
give consideration to the shift in phase, the level of precision with
which the encoder must be manufactured can be relatively low, thereby
improving the mass-producibility of the encoder.
In the foregoing embodiment, although the spring 7 is arranged to cause
force of friction between the shutter 5 and the shaft 3, the present
invention is not intended to be limited thereto. Alternatively, a spring
may cause force of friction between the shutter 5 and the rotary body 2.
FIG. 3 shows, in a vertical section, an embodiment of an image scanner
according to the present invention, and FIG. 4 is a front view of the
construction of that part of the image scanner enclosed by broken lines in
FIG. 3.
The image scanner according to this embodiment includes, as shown in FIG.
3, a light source 22 for projecting light onto an original 21 with an
image to be read, a self-scanning image sensor 24 adapted to receive the
light reflected from the original 21 through a mirror 39 and a lens 23, a
casing 25 accommodating the light source 22, the lens 23 and the image
sensor 24, and serving as an outer shell of the image scanner, a reading
opening 26 formed in a lower portion of the casing 25, a reading start
switch 27 at an upper position of the casing 25, and rollers 28 arranged
with their roller surfaces facing a direction substantially perpendicular
to the self-scanning direction of the image sensor 24 (i.e., to the main
scanning direction), and rotatably supported at lower positions of the
casing 25. The image scanner also includes, as shown in FIG. 4, gears 29
and 30 through which the driving force of the rollers 28 is transmitted in
the mentioned order, and a light-transmission-type encoder 31 engaging
with the gear 30.
The encoder 31 includes a rotary body 33 having, on its periphery, slits 32
permitting light to be transmitted therethrough, a shaft 34 on which the
rotary body 33 is integrally mounted, a shutter 36 being loosely and
swingably fitted on the shaft 34 and having a slit 35, a spring (not
shown) for causing force of friction between the shutter 36 and the shaft
34, a first detector 37 having a light-emitter and a light-receiver
(neither of them being shown) which are disposed with the slits 32 of the
rotary body 33 positioned therebetween, and a second detector 38 having a
light-emitter and a light-receiver (neither of them being shown) which are
disposed with the slit 35 of the shutter 36 positioned therebetween. The
first detector 37 is mounted on a substrate 40 and is covered with a
chassis 41, while the second detector 38 is mounted on another substrate
42. The swinging range of the shutter 36 is limited by the abutment of an
end portion 36a of the shutter 36 on the chassis 41 as well as the
abutment of another end portion 36b of the shutter 36 on the substrate 40.
With this embodiment, when the user, who is depressing the reading start
switch 27, manually moves the scanner on the original 21, covering the
original 21 in a direction perpendicular to the axis of the rollers 28,
the light source 22 projects light through the reading opening 26 onto the
original 21, and the image sensor 24 receives the light reflected from the
original 21 through the mirror 39 and the lens 23, then outputs a signal
indicative of the read image. During the movement of the image scanner,
the rollers 28 rotate while rolling on the original 21, thereby causing,
through the gears 29 and 30, the shaft 34 and the rotary body 33 of the
encoder 31 to rotate. The encoder 31 operates, in a manner similar to the
encoder shown in FIGS. 1 and 2, to detect the amount of and the direction
of the rotation of the rollers 28, that is, to detect the amount of and
the direction of movement performed by the image scanner relative to the
original 21 in the sub-scanning direction, then to output detection
signals.
Subsequently, the image signal and the detection signals are stored, in
accordance with the direction of movement of the image scanner, in an
image memory of the associated host computer, such as the image memory 47
of the host computer 46 shown in FIGS. 5 (a) and 5 (b). At this time, if
the direction of movement of the image scanner is a forward-rotation
direction, as shown in FIG. 5 (a), data expressed by the image signal are
stored in such a manner that the storing starts from the first line area
of the image memory 47. However, if that direction is a backward-rotation
direction, as shown in FIG. 5 (b), the storing of the data starts from the
last line area of the memory 47 so that the first line area stores the
last-read items of the data. The image data stored in this way are read
while maintaining their relative position, then the read data are output
either as an image displayed on a monitor, such as the monitor 48, or as a
hard copy obtained by a printer, not shown.
According to this embodiment of the image scanner, therefore, it is
possible to obtain a displayed image which is always in the correct
positional relation with the image on the original.
The present invention is not intended to be limited to the above-described.
Alternatively, the order in which the data expressed by the image signal
is stored in the image memory 47 may be fixed whichever the direction of
movement is, and the data expressed by the image signal may be converted
to assume the correct positional relation with the image on the original
when the data is to be displayed on the monitor 48.
Further, if the image memory 47 comprises a video RAM on the monitor 48, it
is possible to display the image-signal data on the monitor 48 without
reading the data from the memory 47.
By virtue of the above-described construction of the
light-transmission-type encoder according to the present invention, it is
possible to detect both the amount of and the direction of rotation.
Further, it is possible to improve the mass-producibility of the encoder
as well as to render the rotary body compact, hence, to reduce production
cost.
The above-described construction of the image scanner according to the
present invention provides, in addition to the above-described advantages,
an advantage in that it is possible to obtain a display image which is
always in the correct positional relation with the image on the original
irrespective of the direction of the movement of the image scanner.
Top